Rapid and sensitive tapered-capillary microextraction combined to on-line sample stacking-capillary electrophoresis for extraction and quantification of two beta-blockers in human urine

A tapered-capillary microextraction ( t Cap-μEx) combining with field-amplified stacking (FASI) method for CE analysis was developed. The t Cap- μ Ex method is based on the construction of a micro solid phase extraction (SPE) column by narrowing the end of a silica capillary from 530   µm (inner diameter) to 20   µm, enabling the packing of 45   µm sorbent particles without a frit. Various parameters that may affect the microextraction and FASI-CE analysis have been investigated and optimized. This study shows that microextraction exhibits advantages of small sample and sorbent volumes (less than 200   μL sample and 2   μL sorbent) and fast extraction time of 6   min. The method was successfully applied for efficient determination of atenolol and metoprolol in human urine samples, with recovery of 93.7–105.5% and RSD (n=3) lower than 8.5%. Twenty-one-fold and nineteen-fold average enhancement of detection sensitivity was achieved for atenolol and metoprolol, respectively, versus the CE method without t Cap- μ Ex and FASI. The method is environmentally friendly and allows reuse of the sorbent at least 8 times without an obvious loss in performance. The results indicate that the proposed method could be potentially applied in a wide range of doping control, clinical, forensic toxicology, food analysis and environmental analyses.